Prince Igor (Knazí Igor) is an opera in four acts with a prologue by Alexander Borodin. The libretto, adapted by the composer from the East Slavic epic The Tale of Igorís Campaign, centers on a 12th-century Russian prince (Igor Svyatoslavich) and his campaigns against the invading Polovtsian tribes. The opera was first performed in St.Petersburg on November 4, 1890. In the USA the opera was first produced at the Metropolitan Opera House, New York, December 30, 1915.
Borodin left the opera incomplete at his death in 1887. Composition and orchestration was completed posthumously by Nikolai Rimsky-Korsakov and Alexander Glazunov. According to the printed score, the opera was completed as follows: Rimsky-Korsakov orchestrated the previously unorchestrated passages from the Prologue, Acts 1, 2, and 4, and the "Polovetsian March" which opens Act 3. Glazunov used what existing material was left to compose and orchestrate the rest of the third act; the often-repeated legend is that he also reconstructed and orchestrated the overture from memory after hearing the composer play it at the piano several times. (In his memoirs, Shostakovich quotes Glazunov as admitting to, in essence, writing the overture based on Borodinís themes; this explanation appears to make more sense, because of the rather complex polyphonic nature of the overture, which would have made it virtually impossible to adequately render on the piano.)
Both the Overture to Prince Igor and the "Polovetsian Dances" (from Act II) are well-known concert standards. Together with the "Polovetsian March", they form the so-called "suite" from the opera.

Libretto by the composer based on Old Russian epos The Tale of Igor`s Raid

Prince Igor, who is about to start on a campaign against the Khan Konchak of the Polovtsians, refuses to heed the warnings of his wife and his people who interpret a recent eclipse as a bad omen. Prince of Galich (Kniaz Galitsky) bribes Skoula and Eroshka to encourage Prince Igor in his determination to depart as he himself wants to usurp Igorís place. Igor unsuspectingly entrusts his wife to his care.

ACT I.

Scene I is laid in the Galich Princeís courtyard, where the people are welcoming him as their prince. A group of young women beg the prince to restore one of their friends whom he has carried off; but he frightens them away. Scene II. The young women appeal to Yaroslavna, Igorís wife, who is lamenting Igorís absence in Putyvl, and while they are relating the story, Galich Prince enters. Yaroslavna questions him as to the truth of their story and he only laughs. Word is brought that Igor and his son have been taken captive, and that an attack upon them is imminent.

ACT II.

The Polovtsian Camp: Vladimir, son of Igor, has fallen in love with Konchakovna, a daughter of Khan Konchak. She is sure her father will consent to the marriage, but Vladimir is doubtful if his father will. Konchak offers Igor freedom if he will promise not to wage war on him again, but he refuses.

ACT III.

Igor learns that an attack is to be made on his city. He escapes. He tries to persuade his son to accompany him, but Konchakovna clings to him, and the father leaves alone. When the Khan learns of Igorís escape, he refuses to pursue, retains Vladimir as a hostage, and marries him to his daughter.

ACT IV.

Igor arrives safely at the city Kremlin, and is welcomed with great rejoicing.†(Note: In the new production by the Kirov Opera under Valery Gergiev, recorded in 1995, a new Mariinsky Theatre edition of the music was used, and the acts were performed in the following order: Prologue, II, I, III, IV, so as to create more alternation between Russian and Polovetsian settings.)